A conventional photo acceptance semiconductor device, such as a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal Oxide Semiconductor) image sensor, for converting an optical signal into an electric signal has a semiconductor element or the like packaged and sealed in a hollow package made of ceramics, plastics or the like, in order to prevent moisture, contaminant and the like from entering the semiconductor element from the outside.
FIG. 6 is a sectional view schematically illustrating a structure of a solid-state imaging device as an example of a conventional photo acceptance semiconductor device. The solid-state imaging device 100 includes: a circuit substrate 101 serving as a base; a solid-state imaging element (photo acceptance element) 102; and a covering body 104 attached via an adhesive section 103 on the circuit substrate 101 so as to cover the solid-state imaging element 102. The solid-state imaging device 100 constitutes a hollow package having a hollow section in the covering body 104. The solid-state imaging element 102 is disposed in the covering body 104. In the covering body 104, a transparent covering section 105 is disposed opposite to the solid-state imaging element 102. The transparent covering section 105 is attached to the covering body 104 via an adhesive section 106. Between the transparent covering section 105 and the circuit substrate 101 (solid-state imaging element 102), a space S is formed. The circuit substrate 101 is made of ceramics, glass epoxy, or the like, and the circuit substrate 101 and the solid-state imaging element 102 are electrically connected to each other via a bonding wire 107. The covering body 104 supports a lens barrel 108 positioned at an internal center of the covering body 104, and the lens barrel 108 supports lenses 109 positioned inside the lens barrel 108.
In the solid-state imaging device 100 of FIG. 6, the covering body 104 is disposed above the circuit substrate 101 via the adhesive section 103, and the solid-state imaging element 102 is stored in the covering body 104. Thus, it is difficult to make the solid-state imaging device 100 smaller.
Patent Document 1 discloses a solid-state imaging device which can be made smaller. FIG. 7 is a sectional view of the solid-state imaging device of Patent Document 1. The solid-state imaging device 200 is arranged so that a transparent covering section 205 is bonded to a solid-state imaging element 202 via an adhesive section 203. Further, the solid-state imaging element 202 and the transparent covering section 205 are molded with a poromeric mold resin 207 so that a surface of the covering section 205 is exposed. Further, a lens barrel 208 supporting a lens 206 is bonded to the mold resin 207 via an adhesive section (not shown). In the solid-state imaging device 200, the solid-state imaging element 202 does not have to be stored in the lens barrel (covering body) 208, so that the solid-state imaging device 200 can be made smaller than the solid-state imaging device 100.
In the solid-state imaging device 200 of FIG. 7, a hollow section 209 is formed between the solid-state imaging element 202 and the transparent covering section 205. The hollow section 209 is a tightly closed space, so that condensation may occur on an internal face of the covering section 205.
Patent Document 2 discloses a solid-state imaging device having an air path as measures for preventing occurrence of condensation. FIG. 8 is a plan view (top view) illustrating a partial arrangement of the solid-state imaging device 300 of Patent Document 2. FIG. 9 is a cross sectional view taken along C-C of the solid-state imaging device 300 of FIG. 8. As illustrated in FIG. 9, the solid-stated imaging device 300 of Patent Document 2 is arranged so that a hollow section 309 is formed between a solid-state imaging element 302 and a transparent covering section 305, so that condensation may occur on the internal face of the covering section 305. Thus, as measures for preventing occurrence of condensation, an air path is formed in the adhesive section 303 via which the solid-state imaging element 302 and the transparent covering section 305 are bonded to each other.
Specifically, as illustrated in FIG. 8, the solid-state imaging device 300 is arranged so that an air path 311 extending from the hollow section 309 to the outside is formed. The adhesive section 309 occupies a larger area than the transparent covering section 305, and the air path 311 is formed in the adhesive section 303 so as to be positioned outside the covering section 305. This air path 311 allows a surface of the solid-state imaging element 302 to be under the same condition as ambient air, so that it is possible to prevent occurrence of condensation in the covering section 305. Further, the air path 311 has a complicate shape, thereby preventing water from entering the hollow section 309 via the air path 311.
However, according to the arrangement described in Patent Document 2, when converting an optical signal received by the solid-state imaging element into an electric signal, noises of unknown origin occur, and the noises result in a strip-shaped contrast difference on the screen. This was found by the present inventors.
[Patent Document 1]
Japanese Unexamined Patent Publication Tokukai 2004-296453 (Publication date: Oct. 21, 2004)
[Patent Document 2]
Japanese Unexamined Patent Publication Tokukai 2005-322809 (Publication date: Nov. 17, 2005)